A novel exopolysaccharide-producing bacterium from traditional rice wine koji in China: Whole genome sequencing, exopolysaccharide isolation and bio-functional properties assessment

An exopolysaccharide (EPS)-producing bacterium, identified as Weissella cibaria based on 16S rDNA sequencing, was isolated from Chinese traditional rice wine koji. Whole-genome sequencing (WGS) revealed 2261 core genes and 3 plasmids, with 95 carbohydrate-active enzymes identified in the genome. The EPS produced by W. cibaria ZJU.1 was primarily composed of glucose, with a molecular weight of 144.5 kDa, as determined by high-performance anion-exchange chromatography (HPAEC) and high-performance gel chromatography (HPGPC). Structural analysis indicated that the EPS predominantly consists of α-(1→6) glycosidic bonds (88.32%) and α-(1→3) branches (11.68%). Microscopic examination revealed an interleaved fibrous structure at low concentrations and a lamellar structure at higher concentrations. Thermal analysis demonstrated good stability, with the carbon ring structure intact up to 264.12°C. Furthermore, the EPS exhibited excellent dispersion stability and rheological properties at higher concentrations. Activity prediction using a zebrafish model suggested potential therapeutic benefits, including alleviation of diabetes, anti-tumor, and anti-epileptic effects. This study highlights the promising food and pharmaceutical applications of W. cibaria ZJU.1 EPS.